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Date: Fri, 14 Jun 2013 16:00:28 -0700
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Subject: Re: [PATCH] PCI: Remove not needed check in disable aspm link
From: Yinghai Lu <yinghai@kernel.org>
To: Matthew Garrett <matthew.garrett@nebula.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
        Roman Yepishev <roman.yepishev@gmail.com>,
        Jiang Liu <jiang.liu@huawei.com>, "Rafael J. Wysocki" <rjw@sisk.pl>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Maxim Levitsky <maximlevitsky@gmail.com>,
        Jussi Kivilinna <jussi.kivilinna@iki.fi>
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On Fri, Jun 14, 2013 at 3:48 PM, Matthew Garrett
<matthew.garrett@nebula.com> wrote:
> On Fri, 2013-06-14 at 15:40 -0700, Yinghai Lu wrote:
>> On Fri, Jun 14, 2013 at 3:27 PM, Matthew Garrett
>> <matthew.garrett@nebula.com> wrote:
>> > On Fri, 2013-06-14 at 15:17 -0700, Yinghai Lu wrote:
>> >
>> >> after those two patches, it aspm_disabled is set, via _osc early,
>> >> pre-1.1 devices aspm register will be touched even aspm_force is not specified.
>> >
>> > I don't follow. We were previously automatically disabling ASPM on
>> > pre-1.1 devices even if _OSC didn't give us control.
>>
>> I don't think so, we just moved _OSC support/control setting before pci scan
>> in 3.8 and revert that in v3.9.
>
> Right, sorry, I don't mean _OSC, I mean the FADT flag. We were
> previously automatically disabling ASPM on pre-1.1 devices even if the
> FADT flag was set.

so in that case aspm_disabled, never get set.
booting path: pcie_aspm_init_link_state will not touch aspm on pre-1.1 devices.

late, FADT checking will cause pcie_clear_aspm() get called, it will
call __pci_disable_link_state, and because following line in
pcie_aspm_link()
        /* Nothing to do if the link is already in the requested state */
        state &= (link->aspm_capable & ~link->aspm_disable);
        if (link->aspm_enabled == state)
                return;
aspm in pre-1.1 devices still does not get touched.

Maybe I miss something.

Thanks

Yinghai